Someone Explain Gear Ratio Pro's and Cons
 

I'm ordering an F150 XLT 4x4 Supercab with a 4.6 manual. What gear ratio would you recommend? I'll only be pulling a 17 foot aluminum bass boat or small utility trailer. Also, any comments on engine size would be appreciated. I waited too long to order a 2000 model so now I'm getting the 2001. The benifit is that the hp of the 4.6 is being upped to 240. I'm concerned about gas mileage but also would like to be able to pass vehicles on the road besides small mopeds and amish buggies. Any comments would really be appreciated. (Also, how do you put little smilely faces in the text your're typing? I've seen this on several posts and think it's neat.)
Thanks
Clarke

Smile faces are in the same area that you found your question mark (message icon). I'm glad that the new engine is 240HP, that puts it near the 5.4 (more HP = always good). I tried to answer some of your gear questions in your "driveline" memo.

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2000 F-150 XL,RC,LB,5.4,4R70W,3.55LS,
4-wheel disc/ABS,Chestnut/Parchment,
Ford bedliner & gas/wheel/spare locks,
3" cold air box modification,Superchip,
Dynomax ultra-flow welded 3" cat-back.

I myself have a 98 f-150 with the 4.6L. My truck has the 3.55LS gearing. I do have an automatic and find the truck has enough power to do the middle weight towing that I do. 2 place snowmobile trailer about 1500 pounds, OD used all the time, and our 3,000 pound boat that I tow in OD on flat to moderate hills, bigger hills require me to shift the truck out of overdrive. If I were going to tow more often or more weight, I would go with the 5.4. I average about 17 mpg empty on the highway, about 14-15 towing the toys.

When towing ALWAYS go with the bigger engine! THERES NO REPLACEMENT FOR DISPLACEMENT!!! -Lingenfelter

The smaller engine will have to work harder to accomplish the same tasks. Working harder can mean MORE FUEL too! It definately means MORE WEAR!

ALWAYS get one with a towing package!

Use synthetics all around and buy a engine and trans oil cooler. I recommend the "Perma-cool" http://www.perma-cool.com/Catalog/Cat_page12.html ! This is the cooler I use.

Usually the towing package comes with the better rear. But you want the 3.73 for towing!

Mild disagreement -- you can pull a boxcar with a Briggs & Statton with the right set of gears.

But since you can't get them in your new truck, I'll go with Rand's recommendation (get the 3.73LS).

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Y2K™

Toreador Red, Keyless XLT SC SB 5.4L E4x4 4wDisc/ABS, 3.73LS, Skid, HD 7700# Towing, LT-245's on Chrome, Tube-Steps, Captain's, 6CD, Tonneau, named: "Nick"

I have a 97 4.6 and it is a very weak engine. I drove a 4.8 Chevy and it must have 50 more hp than my truck. I also have a 3.27 gear which is a good choice but more hp would be even better. Take my advice and get a Chevy.

LarryS,

The GM trucks come standard with a 3.73 rear-end gear with 4.10 optional. That will certainly give better performance than a 4.6 with a 3.08 gear. Towing performance comes from torque, not horsepower produced above 4500rpm like the GM engines are tuned to produce. The 4.6 puts out more torque at a lower RPM than the 4.8.

Your gears are still way too tall if performance is a priority...3.27s are more suited to the Mustang that you are towing than the tow vehicle. The torque peak of the 4.6 is at 3250 rpm...if you are after performance select a rear-end gear that places your 3rd gear rpm at 3250 rpm at your favorite highway speed. With the GM trucks and 4.10 gears, they are geared pretty close to this formula.

[This message has been edited by RPFB (edited 06-22-2000).]

True, you can use various methods to get a small amount of torque to move a WHOLE lot of weight... But we're talking about apples here!

From what Ford has to offer!!!!! Get the bigger engine with the biggest ratio difference! Typically truck engines produce most of there torque at lower RPMs. Just so happens the 5.4 produces 350 (lb-ft) @ 2500 RPM where as the 4.6 produces 290 (lb-ft) @ 3250. Now you guess which engine is gonna do a better job with 3.73s???

RATIO explained:

a 3.73:1 ration means basically for every revolution your rear tires make, your drive-shaft has turned 3.73 revolutions!

PROS:

Your engine will hit its peak torque range quicker with less distance traveled!

Engine can pull weight much easier!

Transmission NO COOKY!

CONS:

Typically when you hit peak torque early you can run into problems with tire spin...
Depending on gearing! But you need that torque to get the weight moving quickly! AND when you have an extra 500 lbs of weight on the bumper, its usually not a problem.

ANALOGY:

You and I are 6' tall, 180 lbs, and equal strength. We are given 2 identicle 21 speed bicycles and asked to race from A to B. You are asked to start out in 5th gear, and I'm asked to start out in 1st. I will easily win the race because I will be able to move my weight and the bicycles weight much easier, thus much quicker. HOWEVER, given enough distance you would pass me. Hence, winning in a longer distanced race.

Now ask us to pull some weight or climb a hill! Screw the distance, I'LL KILL YOU!

CURVE BALL:

This can get tricky when you get into performance vehicles. My Camaro (400 HP LT-1) spun a lot easier with the 2.73s than it did with the 3.73s... Basically once you hit a point of power that can easily move the weight with any gearing choice, the gearing wanting to make the rear tires travel the farthest will spin (2.73s)!

Becuase the new Camaro's have LS-1 motors with a torque and HP curve VERY differently than that of the LT-1, same car reacts to gearing VERY differently! The 2.73's where dogs with the LT-1 but well suited for performing with the LS-1....

Are you confused?

FACTORS: Engine HP and TORQUE curves, weight, tires, gearing!

TRUCKS: Forget about it! Get the biggest ratio difference, PERIOD!

[This message has been edited by Rand (edited 06-23-2000).]